The present invention relates to a hinge device having a torsion bar with which a rotatable component is connected to a stationary component.
This type of hinge device is used on a compact, stool, car dashboard or the like, of which lids are rotatable components. The rotatable components are energized to the opening direction with a torsion spring. One of this type of hinge device was disclosed in a Japanese Patent Application No. 63-331955 (Japanese Patent No. 2-178,480, Jul. 7, 1990 by the present applicant.
In FIGS. 9 and 10 showing a conventional hinge device, a rotatable component 1 opens and closes in relation to a stationary component 2. In this case, a rotation of the rotatable component is performed around a shaft element 3 comprising a stationary shaft 4, a rotatable shaft 5 and torsion bars 6 fastening between them, the stationary shaft 4 comprises a supporting portion 4b integrally connected to a shaft portion 4a. The shaft portion 4a is unrotatably inserted into the stationary component 2 and the supporting portion 4b is rotatably inserted into the rotatable component.
On the other hand, the rotatable shaft 5 comprises a connecting portion 5b having a plurality of serrations 5a on an outer surface thereof and a cylinder portion 5c coaxially formed on the opposite side of the connecting portion 5b, between which a flange portion 5d is formed. The connecting portion 5b with serrations 5a is fitted into the serrated inner wall of the rotatable component 1, then the rotatable shaft 5 is integrally connected to the rotatable component 1. Then, a cylinder portion 5c of the rotatable cylinder 5 is rotatably supported by a cylinder portion 7a of an adjusting shaft 7 fixed on the stationary component 2 by serrations 7b formed on an outer surface thereof.
Gaps between the cylinder portion 5c of the rotatable shaft 5 and the cylinder portion 7a are filled with high viscosity grease (not shown).
The rotatable component 1 is energized by the torsion bars 6 in the opening direction. However, the rotatable component 1 rotates at a low speed because of the high viscosity of grease.
The adjusting shaft 7 can be applied an initial torque by adjusting the rotatable shaft 5 as follows:
Firstly, the serration joint between the serrations 7b of the adjusting shaft 7 and the stationary component 2, and the other serration joint between the connecting portion 5b of the rotatable cylinder 5 and the rotatable component 1 are disengaged keeping the stationary shaft 4 partially inserted into the stationary component 2. Then, a new angular difference is made between the rotatable component 1 and the rotatable shaft 5 by engaging a dog clutch 5e and inserting the serrations 5a of the rotatable shaft 5 into different serrations of the rotatable component 1.
However, in the aforementioned conventional hinge device, it is necessary to have a process for forming the shaft element 3 by inserting both ends of the torsion bars 6 into the stationary shaft 4 and the rotatable shaft 5. Other processes are necessary to form the serrations on the rotatable component 1 and the stationary component 2 so that the rotatable shaft 5 and the adjusting shaft 7 are fitted into the rotatable component 1 and the stationary component 2 respectively. Accordingly, too many processes are needed.
After applying an initial torque on the torsion bars 6, the rotatable shaft 5 and the adjusting shaft 7 must be inserted into other angular position of serrations. However, it is not easy to insert the rotatable shaft 5 and the adjusting shaft 7 already tensioned by the torsion bars 6 into other angular position of serrations, because there is a light angular difference between the serrations.
Further, in the above conventional hinge device, both ends of the torsion bars 6 are fixed on the stationary shaft 4 and rotatable shaft 5 which reduced an effective length of the torsion bars 6. Therefore, in order to obtain an increased torsion, it is necessary to add a plurality of torsion bars and it causes an increase of weight.
In addition, in order to improve a damper effect thereof, it is necessary to extend the lengths of rotatable shaft 5 and adjusting shaft 7 in the axial direction, or to increase cylindrical portions of the both shafts 5 and 7, which are inserted alternately. In the former, the damper mechanism is formed on only one side, prejudicing a total balance. In the latter, it is difficult to apply on a small shock absorber, not permitting a free design of products.